The present invention relates to a slide-type writing instrument having a drying-prevention device, and more particularly, to a slide-type writing instrument having a drying-prevention device, wherein the sealing ability and durability of a sealing member are greatly improved to consistently prevent evaporation of ink or drying of a pen tip of the writing instrument using highly-volatile ink, such as a highlighter, a marker, a magic marker, a plus pen or the like.
In general, writing instruments refer to magic markers, highlighters, markers or the like in addition to ballpoint pens, and most of them are provided with detachable sealing caps for preventing ink from being dried at pen tips of the writing instruments.
These writing instruments may be largely classified into a fixed-type writing instrument employing a fixed pen tip and a cap (also referred to as “lid”), a rotation-type (screw-type) writing instrument in which a portion of a pen tip is come out along a spiral pipe by partially rotating a shaft, a knock-type writing instrument in which a pen tip comes out by a movement of a spring in response to pressing of a portion of a shaft, and a slide-type writing instrument in which a pen tip is slid to come in and out.
A sealing member of the slide-type writing instrument has an advantage in that a user can use the writing instrument without any inconvenience related to opening and closing of a separate lid. However, this sealing member has a disadvantage that since it is simply a pen tip-passing hole through which a pen tip comes in and out and which is provided at a one end of the writing instrument, this sealing member is limitedly applicable only to writing instruments using non-volatile or low-volatile ink such as oil-based ink or the like.
On the contrary, when pen tips of marker pens, white pens, water-based pens, highlighters or the like using highly-volatile ink remain in air for a long time, ink or the like is dried, whereby the useful life of the writing instruments may be shortened or deteriorated. Therefore, although there is inconvenience in use, lids are opened and closed to use the writing instruments.
Accordingly, Korean Publication Patent No. 10-1995-0000776 (Lidless writing instrument having drying-prevention device) discloses a configuration in which when a pressing portion of a slide-type writing instrument is pressed, a cover for covering a pen tip portion is opened, and when the pressing portion is pressed once again, the cover is closed and seals the writing instrument to prevent drying of ink.
In addition, Korean Utility Model Registration No. 20-1989-0003644 (Capless writing instrument) discloses a configuration in which when a knock portion is pressed, a pen tip breaks through an elastic body provided on an inner barrel and then is exposed to allow a pen to be used, and when the pen tip is returned to its original position by releasing or re-pressing the knock portion, incised portions of the elastic body are brought into contact with each other and then closed, thereby preventing the pen tip from being dried.
However, this configuration has disadvantages in that the incised portions of the elastic body may be plastically deformed due to friction caused by frequent uses and a sealing force is also deteriorated due to frequent friction.
Meanwhile, the invention disclosed in Korean Patent No. 10-1455958 was conceived by the present inventor and granted as a patent. The patent proposes a slide-type writing instrument having a drying-prevention device, wherein when a knob is simply pressed, a cover portion for sealing a pen tip is opened so that the pen tip protrudes, whereas when the knob is released, the pen tip is retreated into an interior of the writing instrument and the cover portion is automatically closed to prevent the pen tip accommodated in the interior of the writing instrument from being dried.
For the drying-prevention function of such a writing instrument, the performance and durability of the sealing member that is opened or closed in response to an operation of causing the pen tip to come in or out and maintains airtightness in a state where the pent tip is accommodated inside are very critical.
However, the invention disclosed in Korean Patent No. 10-1455958, which was conceived by the present inventor and granted as a patent, was considered to have a limitation on maintaining a precise airtight state between a circular end of a sealing member and a cover hingedly connected thereto.
At the beginning of use, there was no great problem in maintaining a sealing performance between the circular end of the sealing member and the cover. However, there were disadvantages in that when the writing instrument is repeatedly used, a minute gap is formed at a position where the cover is in contact with the end of the cylindrical sealing member, which results in loss of airtightness and gradual deterioration of the sealing performance. Particularly, as for marker pens, white pens, water-based pens, highlighters pens, and the like, which use highly-volatile ink, when these writing instruments are left for a long time, there is concern about a phenomenon in which a volatile component escapes to the outside through the minute gap so that ink or the like is dried up may occur.